Electrical resistor



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' ELEGTRICAL REsIsToR Filed Nov. 23 1928 -2 Sheets-Sheet l /fiIHIIHIIIIHIII A if C: ri fag ki in ,Wm/y /e Y .l 1mm l un. f g .W j@

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mesa-J Apr. is, 1933 l UNITED STATES ,PATENT oFFrcE LYNDE BRADLEY, FMILWAUKEE, WISCONSIN, ASBIGNOB, BY IESNE ASSIGNmTB, :JTO ALLEN-BRADLEYOOMPANY, OF MILWAUKEE, WISCONSIN, A. CORPORATION 0I' 'WISCONSIN'ELECTRICAL RESISTOB lApplication med November 23, 1928. Serial I0.321,386.`

This invention relates to certain new and useful improvements inelectrical resistors adapted particularly for use as voltagedividers orpotentiometers.

Many types of variable resistors adapted for use as potentiometers havebeen produced in the past, all of which however had an unchangeabledefinite ohmic limit and, therefore, this invention has as one of itsob]ects to provide a new and improved potentiometer having means wherebyits effective range may be readily adjusted.

Another object of this invention resides in the provision of apotentiometer which inis substantially equal to the mean or averageresistance the potentiometer is to maintain.

Another object of this invention is to provide a potentiometer having Aafixed resistance readily detachably connected across its end terminalswhereby the potentiometer effective range may be varied in accordancewith different requirements. y

A further objectv of this invention resides in the provision of animproved resistor or potentiometer in which infinite variations of itsresistance values may be obtained.

And a still further object of this invention resides in the provision ofimproved means for simultaneously and inversely varying the resistancevalue of the two units of a potentiometer.

With the above and other objects in view which will appear as thedescription proceeds, my invention resides in the novell construction,combination and arrangement of parts substantially as .hereinafterdescribed and more particularly deined by the appended claims, it beingunderstood that such changes in the precise embodiment of the hereindisclosed invention may be made' as come within the scope of the claims.

In the accompanying drawings I have illustrated one complete example ofthe physicludes a fixed resistance the value of which' Aaccompanyingdrawings, in which like nuv cal embodiment of my invention constructed,according to the best mode I have so far devised for the practicalapplication of the l l l l o v Figure 3 is a cross sectional view takenvthrough Figure 1 on the plane of the line F igurel 4 is a diagrammaticview illustrating one application of my improved potentiometer, and lFigure 5 is a view similar to Figure 4 i1- lustrating anotherapplication thereof.

Referring now more particularly to the merals designate like partsthroughout the several views, 5 represents the body or housing of myimproved potentiometer which lis preferably formed of insulatingmaterial and as a pair of arallel wells 6 and 7 extending downwardly romits upper surface. Lining the cylindrical walls of the wells 6 and 7 aremetal sleeves 8 the upper peripheries of which are ared outwardly andextend a slight distance above the top surface of the body for a urposeto be later described.

, assing through the bottoms of the wells are Contact members 9 and 10having enlarged heads received in recesses 11 in thebottoms of thewellsand having stems extending through apertures 12 communicating withthe recesses 11 connected at their outer ends with terminal members 13and 14 by riveting or the like. The terminal members 13 and 14 aredisposed in correspondingly shaped recesses 15 formed in the under sideof the body .5, and extend beyond the opposite sides of the body toprovideterminal lugs 16 and 17 on one side and resistor supports 18 and19 on the other side for a purpose later described.

Resistor elements 2O in the form of powdered material having the desireddegree of conductivity are positioned in the wells 6 and 7 to beselectively compressed by plungers 21 and 22 working in the wells 6 and7 respectively, to vary their resistance. .The plungers each consist ofspaced discs 23 and 24 having a felt or other like ldisc 25 o greaterdiameter therebetween to frictionally engage the sleeves 8 in the wellsand prevent rotation of the plungers, the plunger units being heldtogether by rivets or the like 26. The upper disc 23 of each plunger isprovided with a key hole slot 27 in which the grooved ends 28 ofactuating' members 29 and 30 are engaged, to provide means forlongitudinally moving the plungers.

The actuating members 29 and v30 consist of micrometer screws havingsquare heads 31 and 32, respectively, and threaded in suitableaperturesin a plate 33 positioned across the top-of the bod-y 5 and closing thewells 6v and 7 and the flared peripheriesof the metal linings 8 of thewells being disposed slightly above the top of the body member are thuselectrically connected with the metal plate 33.

The square heads 31 and 32 of the actuating members 29 and 30 areslidably received in square openings in meshed pinion gears 34 and theactuating member 29`has a stem 35 extending outwardly to mount a. knobor the like 36 whereby simultaneous and opposite rotation of theactuating members threads one into and the other out of its respectiveaperture in the plate 33. As the direction of rotation of the actuatingmembers 29 and 30 is at all times opposite, it lwill be readily apparentthat when one is threaded into its aperture to compress the resistorlelement within its well, the other is threaded outward of its apertureto relieve the pressure on the resistor element within its respectivewell, thus decreasing the resistance of one well and increasing theresistance of the other.

A cover member 37 having the lower edge of its side walls recessed toprovide a shoulder 38 and a peripheral ange 39 is fitted over the plate33 with its flange extended therebelow to engage over the adjacent upperedge ofbody 5 and maintain the parts against shifting, rivets or othermeans 40 extending through aligned apertures in the cov'er, plate 33andthe body 5 retain the several parts in their proper assembled position.Y

The rivet 40, positioned at lthat side of the device from which theterminals v1.6 and 17 project, preferably has a tight fit in the' plate33 to `form an electric contact therewith and a neutral or middleterminal 41 `disposed in a recess 42 formed in the under side of thebody member forms a washer for the lower end of the rivet and is thuselectrically connected therewith land through the plate 33 with themetal sleeves 8 in the wells 6 and 7.

The cover member is apertured in axial alignment fwith the `well 6, asat 43, to receive a mounting bushing 44 adapted to be passed through anaperture ina panel, not shown, to which the device is secured by alclampnut 45 threaded on the bushing 44.

in electrical connection with the unit terniinals 49. The value of theresistance unit is such as to be substantially equal to the mean oryaverage resistance `the potentiometer is in'- tended to maintain and inthis manner it is only necessary to replace the unit 48 to change therange of the device, which, therefore, provides the potentiometer withan unlimited range.

The circuit from the middle terminal 41 to either of the terminals 16and 17 is through the adjacent rivet 40, the plate 33, to the cups 8,through the resistance units 20 within the Wells, where the value of thecurrent is adjusted, and through the Contact members 9 and 10 to theterminals 16 and 17.

The uses to which a-device of this nature may be adapted .are numerousand in Figure series with the plate voltage'of the first ther# mionictube 51.

From the foregoing description, taken in connection with theaccompanying drawings,

lit will be readily apparent to'those skilled in the art to whichan-invention of the character described appertains, that I provide a newand novel potentiometer or variable resistor which functions eiiicientlythroughout ,prac-i tically an unlimited range andi-n which in# initelysmall variations of the resistance -values of its two circuitv branchesmay .be obtained.

' What I claim as my invention is.:

1. A potentiometer, comprising two variable resistors electricallyconnected at one of their ends and having their resistances variableunder pressure, means for simultaneously and inversely varying theresistances of said ln this instance, the terminals 16 resistors, afixed resistor, and common terseries across the terminals so that thesum of vminals for the other .ends of the variable rebothis alwaysconstant, and a fixed resistor sistorsv and the fixed resistorwherebythe mounted on Vthey outside of. the supportin lixed resistorelectrically bridges said other member and electrically bridging thespace ends of the variable resistors, said common terminals yto delinethe effective resistance 7o terminals being adapted to have conductors'across the terminals, the value of said-fixed attached thereto toconnect the potentiometer resistor beingchosen to adapt the potentloinan electric circuit, and said fixed resistor meter to a particularcircuit requirement. having a resistance value to adapt the poten- Intestimony whereof I have hereunto tiometer to a particular circuitrequirement. aiixed my signature. 75

2. A potentiometer comprising a body member having a pair of wells, aresistance LYNDE BRADLEY. element disposed in each well and composed ofcompressible material the resistance of x which is adjustable bpressure, plungers 80 movable into and out o ysaid wells for a plyingvarious de rees of pressure to sai elements, means or simultaneously andoppositely moving the plungers, contact members electrically connectedwith the resistance ele- 85 ments within the Wells, and a fixed resistorcarried by and electrically/connected with the contact members wherebythevalue of the fixed resistor defines the effective resistance value ofthe potentiometer, said con- 90 tact members being adapted to haveconductors connected therewith to connect the potentiometer in anelectric circuit, and the value of the'fixed resistor being chosen to yadapt the potentiometer to a particular cir- 95 cuit requirement.

, 3. In av rheostat, a supporting body, -an adjustable resistor elementcarried by the supporting body, terminals for the adjust'- l ableresistor element rojectin from one 100 side of the supporting ody, and aixed'resistance element supported jointly by the terminals and said sideof the body, the lterminals being adapted to have conductors con- 40nected therewith .for connecting the rheostat 105 in an electriccircuit, and said fixed resistance .elen'ient being electricallyconnected with the terminals to dene the overall value of the rheostatand ladapt the same toa particular circuit requirement.

4. In a potentiometer, spaced terminals",`v f two electrical resistors,one connected with each terminal, means to simultaneously and Aoppositely vary the individual resistance of p said resistors andconnect the resistors in. v U5 series across the terminals so that thesum of both is always constant, and a fixed resistance mounted on thepotentiometer and connecting the terminals tovdeline the effectiveresistance across the terminals. g '12 5. Apotentiometer comprisin asupporting member having -spaced poc ets,'spaced y terminals each having'a ortion extending i'nto one pocket, a variable resistance element i'neach pocket in electrical connection I 125 with the terminal' parttherein a cover to a close the pockets, means carried bythe cover tosimultaneously and oppositely vary the individual resistance of .saidresistanceA elements and connect the resistance elements inl 130

